Magnetic particles, methods of making, and uses thereof

1. A composition, comprising:

a plurality of magnetic particles, wherein the magnetic particles each independently comprise

a nickel ferrite core having the formula Ni 1−x M x Fe 2+y O 4 , wherein M is at least one of Zn, Mg, Co, Cu, Al, Mn, or Cr; x is 0 to 0.95, and y=−0.5 to 0.5; and

an iron nickel shell at least partially surrounding the core, wherein the iron nickel shell has the formula Fe 2 Ni 1−x M x .

2. The composition of claim 1 , wherein M comprises at least one of Zn, Al, or Co.

3. The composition of claim 1 , wherein the nickel ferrite core has an average grain size of 5 to 100 nanometers.

4. The composition of claim 1 , wherein x is 0.05 to 0.95.

5. The composition of claim 1 , wherein M comprises at least one of Co or Zn.

6. The composition of claim 1 , wherein the plurality of magnetic particles comprises at least one of irregularly-shaped particles, spherical particles, oval particles, rod-shaped particles, flakes, or fibers.

7. The composition of claim 1 , wherein the plurality of magnetic particles has a median D50 particle size of 0.5 to 800 micrometers; and wherein the nickel ferrite core has an average grain size of 5 to 100 nanometers.

8. The composition of claim 1 , wherein the shell has an average thickness of 0.05 to 20 micrometers.

9. The composition of claim 1 , wherein at least a portion of the plurality of magnetic particles are platelets; wherein the platelets have at least one of a longest dimension of 0.5 to 100 micrometers or a platelet thickness of 0.05 to 1 micrometer, with the proviso that the longest dimension is greater than the platelet thickness.

10. A composite comprising:

the plurality of magnetic particles of claim 1 ; and

a polymer.

11. The composite of claim 10 , wherein the polymer comprises at least one of a fluoropolymer, a polyolefin, a poly(arylene ether ketone), a poly alkyl (meth)acrylate, or a poly(ether sulfone); and/or

wherein the composite comprises 10 to 95 volume percent of the magnetic particles based on the total volume of the composite; and 10 to 90 volume percent of the polymer based on the total volume of the composite.

12. The composite of claim 10 , wherein the composite has at least one of

a permeability at 1 GHz of greater than or equal to 1.4;

a magnetic loss tangent of less than or equal to 0.05 at 1 to 3 gigahertz;

a permittivity at 1 GHz of less than or equal to 60; or

a dielectric loss tangent at 1 GHz of less than or equal to 0.

13. An article comprising the composite of claim 10 , wherein the article is an antenna, a transformer, an anti-electromagnetic interface material, or an inductor; and/or wherein the article is a microwave device.

14. A composition, comprising:

a plurality of magnetic particles, wherein the magnetic particles each independently comprise

a nickel ferrite core having the formula Ni 1−x M x Fe 2+y O 4 , wherein M is at least one of Zn, Mg, Co, Cu, Al, Mn, or Cr; x is 0 to 0.95, and y=−0.5 to 0.5; wherein the nickel ferrite core has a nanocrystalline structure; and

an iron nickel shell at least partially surrounding the core, wherein the iron nickel shell comprises iron, nickel, and optionally M,

wherein the plurality of magnetic particles has a median D50 particle size of 0.5 to 800 micrometers; and wherein the nickel ferrite core has an average grain size of 5 to 100 nanometers.

15. A composition comprising:

a plurality of magnetic particles; wherein the magnetic particles each independently comprise

a nickel ferrite core having the formula Ni 1−x M x Fe 2+y O 4 , wherein M is at least one of Zn, Mg, Co, Cu, Al, Mn, or Cr; x is 0 to 0.95, and y=−0.5 to 0.5; and

an iron nickel shell at least partially surrounding the core, wherein the iron nickel shell comprises iron, nickel, and optionally M; wherein the iron nickel shell comprises less than or equal to 5 atomic percent of oxygen based on the total atoms in the iron nickel shell.

16. A method of forming a composition comprising a plurality of magnetic particles of claim 1 , the method comprising:

heat treating a plurality of nickel ferrite particles in a hydrogen atmosphere to form the plurality of magnetic particles having the iron nickel shell on the nickel ferrite core;

wherein the magnetic particles each independently comprise

a nickel ferrite core having the formula Ni 1−x M x Fe 2+y O 4 , wherein M is at least one of Zn, Mg, Co, Cu, Al, Mn, or Cr; x is 0 to 0.95, and y=−0.5 to 0.5; and

an iron nickel shell at least partially surrounding the core, wherein the iron nickel shell comprises iron, nickel, and optionally M.

17. The method of claim 16 , wherein the heat treating comprises heating the nickel ferrite particles to a temperature of 300 to 1,000° C.; and/or wherein the hydrogen atmosphere further comprises least one of nitrogen or argon.

18. The method of claim 16 , where in the hydrogen atmosphere comprises 1 to 10 volume percent of hydrogen and 90 to 99 volume percent of argon or nitrogen.

19. The method of claim 16 , further comprising forming the plurality of nickel ferrite particles by high energy ball mixing; wherein the high energy ball mixing comprises mixing nickel ferrite precursor compounds in a hardened chrome steel vial comprising a plurality of hardened chrome steel balls; wherein a mass ratio of the plurality of hardened chrome steel balls to the nickel ferrite precursor compounds is 20:1 to 40:1 during the high energy ball milling.